There is an image reading apparatus provided with a document feeder, which is called ADF (Auto Document Feeder) for conveying documents from a sheet feed tray through a conveying path to a sheet discharging tray. For example, JP-A-8-85649 discloses a document feeder in which for the purpose of reading a document printed both on the first and second faces, the document is conveyed for reading images on both faces of the document, with the leading end of the document turned back to the trailing end in the course of conveyance.
FIG. 33 and FIG. 34 are pattern diagrams showing a conveyance path of an example of a document feeder for reading images on both sides. As shown in FIG. 33, a plurality of sheets of a document is placed on a sheet feed tray 100, with the first face (page 1) being kept upward. Document P is fed from a feed roller 101 to a conveying path 102. A conveying roller 103 is provided on the conveying path 102, whenever necessary. The document is conveyed by the conveying roller 103, and when passing over a reading position X, the document P is read for the first face by an image reader. When the document P after the first face has been read is detected for the trailing end by a sensor, a discharge roller 104 is halted, with the trailing end of the document being nipped.
As shown in FIG. 34, the discharge roller 104 is reversed to convey the document P to a return path 105. The document P again advances upstream in the conveying direction at the reading position X on the conveying path 102 from the return path 105. Then, on passage of the document P conveyed by the conveying roller 103 over a reading position X, the second face (page 2) is read by an image reader. When the document P is detected for the trailing end by a sensor after the second face has been read, the discharge roller 104 is halted again, with a part near the trailing end of the document being nipped. Thereafter, the discharge roller 104 turns reversely, thereby conveying the document P to a switchback path 105. The document P, which has again advanced from the return path 105 to the conveying path 102, passes, with the first face being opposed to the reading position X. The document P is conveyed on the conveying path 102 and discharged to a sheet discharging tray 106, with the first face kept downward. Thereby, documents are discharged to the sheet discharging tray 106 in the order that they are stacked on the sheet feed tray 100.
Further, JP-A-11-157756 discloses another example of a document feeder for reading images on both faces. In the document feeder, the return path 105 is extended from an upper portion on the conveying path 102 which is approximately in a laterally-faced U-shape, and the terminal end of the return path 105 is opened outside the feeder toward the upper side of the sheet feed tray 100.